Psilocybin biases facial recognition, goal-directed behaviour, and mood state toward positive relative to negative emotions through different serotonergic subreceptors

This double-blind, within-subjects, placebo-controlled study (n=17) investigated if psilocybin causes emotional processing biases to trend away from negative information by activating 5-HT2A (Serotonin) receptors. It was indeed found that psilocybin enhanced mood and shifted emotional bias towards positive information. The 5-HT2A receptors played a crucial role in the effects of psilocybin on emotional processing.

Abstract

“Background: Serotonin (5-HT) 1A and 2A receptors have been associated with dysfunctional emotional processing biases in mood disorders. These receptors further predominantly mediate the subjective and behavioural effects of psilocybin and might be important for its recently suggested antidepressive effects. However, the effect of psilocybin on emotional processing biases and the specific contribution of 5-HT2A receptors across different emotional domains is unknown.

Methods: In a randomized, double-blind study, 17 healthy human subjects received on 4 separate days placebo, psilocybin (215 μg/kg), the preferential 5-HT2A antagonist ketanserin (50 mg), or psilocybin plus ketanserin. Mood states were assessed by self-report ratings, and behavioural and event-related potential measurements were used to quantify facial emotional recognition and goal-directed behaviour toward emotional cues.

Results: Psilocybin enhanced positive mood and attenuated recognition of negative facial expression. Furthermore, psilocybin increased goal-directed behaviour toward positive compared with negative cues, facilitated positive but inhibited negative sequential emotional effects, and valence-dependently attenuated the P300 component. Ketanserin alone had no effects but blocked the psilocybin-induced mood enhancement and decreased recognition of negative facial expression.

Conclusions: This study shows that psilocybin shifts the emotional bias across various psychological domains and that activation of 5-HT2A receptors is central in mood regulation and emotional face recognition in healthy subjects. These findings may not only have implications for the pathophysiology of dysfunctional emotional biases but may also provide a framework to delineate the mechanisms underlying psylocybin’s putative antidepressant effects.”

Authors: Michael Kometer, André Schmidt, Rosilla Bachmann, Erich Studerus, Erich Seifritz & Franz X. Vollenweider

Notes

This paper is included in the meta-analytical review by Galvão-Coelho and colleagues (2021) that found psychedelics to improve mood (for those with mood disorders) both in the short and long term (up to 60 days).